Crossbows have been used for centuries for both hunting and recreation. They are characterized by limbs mounted on a stock with a bowstring that is drawn to store energy that is transferred to a bolt upon firing. Aspects of the present disclosure address different types of crossbow arrangements and assembly aspects.
In some embodiments, the features may be used alone or in combination with reverse crossbows. A traditional reverse crossbow includes limbs mounted to a frame with the limb butt portions closer to the user. The limbs curve outward and away from the user. When cocked, the limb tips are drawn generally inward toward a central portion. When released, the limb tips spring outward, causing the bowstring to travel forward and propel a projectile such as a quarrel. The reverse crossbow arrangement allows the bowstring to be drawn and released to travel a greater distance with a longer power stroke compared to a traditional “forward” crossbow, allowing greater force to be imparted to the projectile.
The concept of a reverse crossbow has been well known for decades, for example as shown in U.S. Pat. No. 3,108,583 to Andis; U.S. Pat. No. 5,630,405 to Nizov; U.S. Pat. No. 4,169,456 to Van House; U.S. Pat. No. 4,766,874 to Nishioka; U.S. Pat. No. 4,879,987 to Nishioka; U.S. Pat. No. 7,328,693 to Kempf, and U.S. Pat. No. 7,938,108 to Popov. These references show a crossbow with limbs inverted to point forward, i.e. limbs that are curved so that their ends generally point toward the front of the crossbow and having a longer power stroke.
Some reverse crossbows have a riser assembly formed of a single crosspiece, which requires that all of the force applied via the limbs is focused through the single crosspiece, which may be close to perpendicular to the limbs. The forces applied by the limbs are effectively applied against lever arms defined by the radius length of the cantilevered ends from a center connection point. In essence the stresses attempt to rotate the lever arm forward or rearward, and the crosspiece alone must withstand the applied stress. When a riser with only a perpendicular crosspiece is used, a stronger and larger crosspiece is needed or less force can be sustained in use.
To reduce stress on the crosspiece, it can be advantageous to use a triangular riser, for example a monolithic triangular riser as taught by Nizov in U.S. Pat. No. 5,630,405. In Nizov's triangular riser, a pair of bracing portions extend from the ends of a perpendicular crosspiece and are angled inward to then connect with the stock and rail. Thus, part of the force applied by the limbs to the riser is transmitted rearward via the angled bracing portions so that the stock and rail assembly may brace the angled portions at the rearward connection points and consequently help brace the crosspiece. In contrast to the crosspiece portion, which is essentially perpendicular to the stock and rail and which may be close to perpendicular to the limbs, the angled portions can be aligned closer to a forward/rearward direction, and can be more closely aligned with the forward and rearward force vectors applied to the riser by the limbs. However, manufacturing a monolithic triangular riser as taught by Nizov can be complex and expensive.